I sent my daughter's in on August 25th with the old photos...didn't read about the change until a few days ago. I'm worried now too.
However, this is my thinking: The new photo specifications come into effect for photos physically dated by the photographer AFTER August 23rd. IRCC allows photos to be used if they are taken within the last 6 months according to the application. So say I had the photos taken in March 2017, they would still be valid under that 6-month rule. I think the new specifications are only for those taking the actual photos after the new change went into effect.
They make the photographer date the photos for a reason. With transportation times (up to 2 weeks with mail coming from the US, much longer if the application is collected from an embassy) and then processing times (mine took a month), it would result in a ton of returned applications if they changed the photo spec without warning and then rejected/returned every application that immediately didn't meet the specifications.
I would strongly believe that the only date that is going to matter is the photograph's listed date,
maybe the date of postmark (because the applications will sit for several weeks before being opened and checked).
If you already sent in the application, its out of your hands at this point. Highly unlikely to be rejected.
If you haven't sent in the application already, you could call the call centre (using the "back door" if in the US), ask the embassy... or, if it's not a huge burden, take the old spec photos back along with the new photo specs to the photographer. Digital photography is super cheap and most places would be willing to re-take/print the photos free of charge.